Directional coupler

Abstract

Directional couplers are used to detect forward power delivered by a power amplifier. Mechanisms are provided herein which improve the accuracy of the power detection in the presence of external noise. Accuracy in power detection can be used to simplify the design of the power control loop.

What is claimed is: 
     
         1 . A coupler, comprising:
 a main branch coil configured to receive current from a monitored circuit and carry the current through the main branch coil;   a coupled branch coil positioned in proximity to the main branch coil and configured to detect an amount of current flowing in the main branch coil via an inductive coupling between the coupled branch coil and the main branch coil, wherein at least one of the main branch coil and coupled branch coil are configured to at least partially reject external magnetic fields that are created by circuit elements other than the main branch coil.   
     
     
         2 . The coupler of  claim 1 , wherein the main branch coil comprises a first sub-coil and a second sub-coil that are interconnected to one another, wherein the first sub-coil creates a magnetic field in a direction that at least partially opposes a magnetic field created by the second sub-coil. 
     
     
         3 . The coupler of  claim 2 , wherein the first sub-coil comprises a polarity that opposes a polarity of the second sub-coil. 
     
     
         4 . The coupler of  claim 3 , wherein the first sub-coil and second sub-coil are interconnected to one another to make a figure-eight configuration. 
     
     
         5 . The coupler of  claim 4 , wherein the coupled branch coil also forms a figure-eight configuration that substantially coincides with the figure-eight configuration of the main branch coil. 
     
     
         6 . The coupler of  claim 4 , wherein the first sub-coil and second sub-coil are substantially the same size. 
     
     
         7 . The coupler of  claim 4 , wherein the first sub-coil and second sub-coil are different sizes and a larger of the first sub-coil and second sub-coil are positioned closer to the circuit elements other than the main branch coil that contribute more external magnetic field to the main branch coil. 
     
     
         8 . The coupler of  claim 1 , wherein the coupled branch coil has current induced therein by a magnetic field created by the current flowing in the main branch coil and wherein the current flowing in the coupled branch coil is used to create a power measurement for the monitored circuit. 
     
     
         9 . The coupler of  claim 8 , wherein the monitored circuit comprises a power amplifier. 
     
     
         10 . A coupling system, comprising:
 a first coil configured to carry a first current and create at least a first magnetic field in response to the first current flowing therethrough;   a second coil configured to carry a second current that is created in response to the first magnetic field passing through the second coil, wherein the first coil and second coil are positioned proximate to one another, and wherein at least one of the first coil and second coil are configured to create a net electromotive force of approximately zero.   
     
     
         11 . The system of  claim 10 , wherein the first coil comprises a first sub-coil and a second sub-coil connected in series with one another, wherein the first sub-coil creates an electromotive force that opposes an electromotive force created in the second sub-coil thereby creating the net electromotive force of approximately zero. 
     
     
         12 . The system of  claim 11 , wherein the second coil also comprises a first sub-coil and a second sub-coil that are connected in series with one another. 
     
     
         13 . The system of  claim 12 , wherein the first sub-coil of the first coil and the first sub-coil of the second coil are substantially the same size and are substantially coincident with one another. 
     
     
         14 . The system of  claim 11 , wherein the first sub-coil and second sub-coil create a figure-eight configuration. 
     
     
         15 . The system of  claim 11 , wherein the first coil further comprises a third sub-coil that is connected in series with at least one of the first sub-coil and second sub-coil. 
     
     
         16 . The system of  claim 10 , wherein the first coil and second coil are both established on a common silicon chip. 
     
     
         17 . An electronic device, comprising:
 an Integrated Circuit (IC) chip, comprising:
 a monitored circuit; 
 a source of electromagnetic interference; 
 a main branch coil configured to receive current from the monitored circuit and convert the received current into a magnetic field; and 
 a coupled branch coil configured to receive the magnetic field created by the main branch coil and in response to receiving the magnetic field create an induced current therein, wherein the induced current flowing in the coupled branch coil is indicative of the current received at the main branch coil from the monitored circuit, and wherein at least one of the main branch coil and coupled branch coil are configured to reject the electromagnetic interference created by the source of electromagnetic interference. 
   
     
     
         18 . The communication device of  claim 17 , wherein the main branch coil comprises a figure-eight configuration. 
     
     
         19 . The communication device of  claim 18 , wherein the coupled branch coil comprises a figure-eight configuration that substantially matches the figure-eight configuration of the main branch coil. 
     
     
         20 . The communication device of  claim 18 , wherein a first loop of the figure-eight configuration and a second loop of the figure-eight configuration are configured to cancel effects of the electromagnetic interference created by the electromagnetic interference.